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Stegosaurus
Stegosaurus is a genus of stegosaurid armoured dinosaur from the Late Jurassic period. Due to its distinctive tail spikes and plates, Stegosaurus is one of the most recognizable dinosaurs, along with Tyrannosaurus, Triceratops, and Apatosaurus. The name Stegosaurus means "roof-lizard" and is derived from the Greek stegos/στέγος-, ("roof") and sauros/σαῦρος, ("lizard"). Information The long and narrow skull was small in proportion to the body. It had a small antorbital fenestra, the hole between the nose and eye common to most archosaurs, including modern birds, though lost in extant crocodylians. The skull's low position suggests that Stegosaurus may have been a browser of low-growing vegetation. This interpretation is supported by the absence of front teeth and their replacement by a horny beak or rhamphotheca. Stegosaurian teeth were small, triangular and flat wear facets show that they did grind their food. The inset placement in the jaws suggests that Stegosaurus had cheeks to keep food in their mouths while they chewed. Despite the animal's overall size, the braincase of Stegosaurus was small, being no larger than that of a dog. A well preserved Stegosaurus braincase allowed Othniel Charles Marsh to obtain in the 1880s a cast of the brain cavity or endocast of the animal, which gave an indication of the brain size. The endocast showed that the brain was indeed very small, maybe the smallest among the dinosaurs. The fact that an animal weighing over 4.5 tonnes could have a brain of no more than 80 grams contributed to the popular old idea that dinosaurs were unintelligent, an idea now largely rejected. Soon after describing Stegosaurus, Marsh noted a large canal in the hip region of the spinal cord, which could have accommodated a structure up to 20 times larger than the brain. This has led to the famous idea that dinosaurs like Stegosaurus had a 'second brain' in the tail, which may have been responsible for controlling reflexes in the rear portion of the body. It has also been suggested that this "brain" might have given a Stegosaurus a temporary boost when it was under threat from predators. More recently, it has been argued that this space (also found in sauropods) may have been the location of a glycogen body, a structure in living birds whose function is not definitely known but which is postulated to facilitate the supply of glycogen to the animal's nervous system. The most recognizable features of Stegosaurus are its dermal plates, which consisted of 17 separate flat plates. These were highly modified osteoderms (bony-cored scales), similar to those seen in crocodiles and many lizards today. They were not directly attached to the animal's skeleton, instead arising from the skin. In the past, some palaeontologists, notably Robert Bakker, have speculated the plates may have been mobile to some degree, although others disagree. Bakker suggested that the plates were the bony cores of pointed horn-covered plates that a Stegosaurus could flip from one side to another in order to present a predator with an array of spikes and blades that would impede it from closing sufficiently to attack the Stegosaurus effectively. The plates would naturally sag to the sides of the Stegosaurus, the length of the plates reflecting the width of the animal at that point along its spine. His reasoning for these plates to be covered in horn is that the surface fossilized plates have a resemblance to the bony cores of horns in other animals known or thought to bear horns, and his reasoning for the plates to be defensive in nature is that the plates had insufficient width for them to stand erect easily in such a manner as to be useful in display without continuous muscular effort. The largest plates were found over the animal's hips and measured 60 centimeters wide and 60 centimeters tall. The arrangement of the plates has long been a subject of debate but most palaeontologists now agree that they formed a pair of alternating rows, one running down each side of the midline of the animal's back. The function of the plates has been much debated. Initially thought of as some form of armour, they appear to have been too fragile and ill-placed for defensive purposes, leaving the animal's sides unprotected. More recently, researchers have proposed that they may have helped to control the body temperature of the animal, in a similar way to the sails of the large carnivorous Spinosaurus or of the pelycosaur Dimetrodon (and the ears of modern elephants and jackrabbits). The plates had blood vessels running through grooves and air flowing around the plates would have cooled the blood. This theory has been seriously questioned, since the closest relative to the common plate-wielding species, Stegosaurus stenops, had low surface area spikes instead of plates, implying that cooling was not important enough to require specialized structural formations such as plates. Their large size suggests that the plates may have served to increase the apparent height of the animal, in order either to intimidate enemies or to impress other members of the same species, in some form of sexual display, although both male and female specimens seemed to have had them. A study published in 2005 supports the idea of their use in identification. Researchers believe this may be the function of other unique anatomical features, found in various dinosaur species. Stegosaurus stenops also had disk-shaped plates on its hips. There has been debate about whether the tail spikes were used for display only, as posited by Gilmore in 1914 or used as a weapon. Robert Bakker noted the tail was likely to have been much more flexible than that of other dinosaurs, as it lacked ossified tendons, thus lending credence to the idea of the tail as a weapon. However, as Carpenter has noted, the plates overlap so many tail vertebrae, that movement would be limited. Bakker also observed that Stegosaurus could have maneuvered its rear easily, by keeping its large hindlimbs stationary and pushing off with its very powerfully muscled but short forelimbs, allowing it to swivel deftly to deal with attack. More recently, a study of tail spikes by McWhinney et al., which showed a high incidence of trauma-related damage, confirms the spikes were indeed used in combat. Additional support for this idea was a punctured tail vertebra of Allosaurus into which a tail spike fit perfectly. Stegosaurus stenops had four dermal spikes, each about 60–90 centimeters long. Discoveries of articulated stegosaur armour show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted. Initially, Marsh described S. armatus as having eight spikes in its tail, unlike S. stenops. However, recent research re-examined this and concluded this species also had four. In-Game Stegosaurus will be in the early access of Prehistoric Kingdom. Category:Stegosaur Category:Herbivore Category:Dinosaurs